This application is related to U.S. patent application Ser. No. 294,153 entitled "Recovery of Glucan by a Divalent Cation Salt in Concert With a Water Miscible Organic Solvent," and U.S. patent application Ser. No. 294,250 entitled "Recovery of Glucan by Employing a Divalent Cation at an Alkaline pH".
The invention relates to a process for the recovery of water soluble biopolymers, in particular polysaccharides, gums, agar, agarose and starch. Further, the invention relates to the recovery of the biopolymers in a solution by adding a polyoxide, in particular polyethylene glycol or polyethylenesorbitan to the biopolymer containing liquid to induce precipitation of the biopolymer.
Many species of bacteria, fungi, plants and algae produce water soluble polysaccharides, gums and starches. Polysaccharides produced by fungi and bacteria generally are obtained by fermentation processes. The biopolymers are then recovered from the broth solution. Biopolymers such as polysaccharides produced by algae, are intracellular macromolecules which are extracted from naturally occurring fresh water or marine mixed cultures. Natural biopolymer gums such as locust bean gum and guar gum are produced and harvested from shrubs and trees generally found in Africa, Asia and India. Typically, the gum is found in the seeds of the plants. The crude gum powder can be hydrated or suspended and then the gum is precipitated from the solution.
The full commercial potential of biopolymers is restricted by high price and costs due to processing and product recovery. Downstream processes, especially in fermentations are usually a multistep batch process that use solvents to precipitate the biopolymer from the broth or solution. Current procedures teach the use of a water miscible organic solvents such as isopropyl alcohol or acetone for the recovery of biopolymers such as water soluble polysaccharides, in particular glucan from fermentation media and other glucan containing solutions. As practiced, the clarified media is concentrated to a flowable viscosity and precipitated with greater than 50% by volume solvent. The precipitate is drained and then successively treated with higher concentrations of the water miscible organic solvent. In the case of glucan-type polysaccharides a minimum of 2 to 3-fold excess of solvent to broth is generally required to adequately precipitate all of the glucan in solution. Alternatively, usable glucans can be recovered and concentrated by more elaborate techniques such as freeze-drying, lyopholization or spray-drying at moderate temperatures of about 150.degree. to 180.degree. C.
U.S. Pat. No. 3,759,896 discloses a process to produce polysaccharides with anti-tumor activity mainly consisting of B-(1-&gt;3)-linked D-glucose residue by obtaining culture filtrates of fungi belonging to Ascomycetes, Basidiomycetes and Fungi imperfect and then purifying the culture filtrate by sequential treatments of acidification, deionization by ion exchange resins and precipitation with a water soluble miscible solvent.
U.S. Pat. No. 4,072,567 discloses a process for producing a glucan by cultivating a Streptococcus microorganism in a liquid medium and recovering the glucan by sedimentation, filtration or sieving. The crude glucan is further processed by dissolving in sodium hydroxide, centrifuging, neutralizing with hydrogen chloride and then washing.
Xanthan gum, an anionic polysaccharide, is a fermentation product of the bacteria Xanthomonas campestris. The polysaccharide is recovered from the fermentation broth by salt precipitation. Known precipitating agents for the polysaccharide include quarternary amine salt precipitation (U.S. Pat. No. 3,119,812); aluminum salt precipitation (U.S. Pat. No. 4,051,317); amine salt precipitation (U.S. Pat. No. 4,254,257) and alkaline precipitation in the presence of divalently cations (U.S. Pat. No. 3,382,229). Known precipitating agents for polysaccharides are calcium ion combined with an alkaline pH, isopropyl alcohol and a quarternary compound, see U.S. Pat. No. 4,053,699.
This invention provides a process for large scale purification and recovery of water soluble biopolymers from a variety of aqueous solutions. It has the advantages of being cost efficient, scalable from laboratory to large process scale and no harsh or hazardous chemicals.
The water soluble biopolymers of polysaccharides, gums and starches are widely used in industrial and food applications. The biopolymers have useful properties such as stability in cold, hot or high salt environments, performance at low concentrations and pseudoplasticity. Applications of the biopolymers in the industrial area include uses as a suspending agent, viscosifier, stabilizer and emulsifier. Applications of the biopolymers in the food industry include uses to improve body and texture, thickening powder, gel stability and emulsification.
It is an object of the instant invention to recover water soluble biopolymers from aqueous solutions. It is another object of the instant invention to recover biopolymers such polysaccharides, gums, agars, agaroses and starches from solution by precipitating the biopolymer from the solution with a polyoxide, such as polyethylene glycol or polyoxyethylenesorbitan.
These and other objects, together with the advantages over known methods shall become apparent from the specification which follows and are accomplished by the invention as herein described and claimed.